Electronic discharge device



June 21, 1949. w Q BROWN ELECTRONIC DISCHARGE DEVICE 2 Sheets-Sheet 2 Filed March 20, A1945 Patented June` 21, 1949 UNITED STATES PATENT CFFICE ELECTRNIC DISCHARGE DEVICE Application March 20, 1945, Serial No. 583,787

9 Claims. l

This invention relates to magnetrons of the type having a plurality of anode elements providing a plurality of circuits intended to oscillate at the same frequency and thus jointly contribute to the effective output of the magnetron.

Devices of the type to which the invention relates comprise a plurality of anode arms providing capacitances therebetween and connected by an inductance completing the oscillating circuits. The inductance is commonly provided by the metallic walls of the envelope enclosing the evacuated Space of the tube. Such devices, as heretofore constructed, involve structural diiculties particularly with respect to the tuning, for since the oscillating circuits are disposed entirely within the evacuated space of the tube, these can be tuned only by resort to flexible walls or to the introduction of additional tuning circuits.

It is an object of the present invention to provide a magnetron which may be tuned externally of the evacuated Space, and without the necessity for providing additional tuning circuits.

It is a further object of the invention to simplify the construction oi such devices whereby they may be more easily manufactured than has heretofore been possible.

The above and other objects and features of the invention will be made fully apparent to those skilled in the art from a consideration of the following detailed description taken in conjunction with the accompanying drawing in which:

Fig. 1 is a longitudinal section through one em bodiment of the invention;

Fig. 2 is a section taken on the line -E of Fig. 1; and

Fig. 3 represents a longitudinal section, with parts in side elevation, through another embodiment of the invention.

Referring to the drawing and rst Figs. l and 2 thereof, the magnetron there shown comprises a body portion I which in this instance is a hollow spheroid of magnetic material of high coercive force such as Alnico. The body I is iiattened at the pole thereof and is provided with bores 2 and 3 extending therethrough. The body I is so magnetized that these bores constitute the opposite poles of the magnet. Disc-shaped pole pieces 4 and 5 of cold rolled steel or other suitable magnetic material close the bores 2 and 3 making a tight fit therewith. Coextensive with the internal end faces of pole pieces 4 and 5 are a pair of discs I and 8 of Kovar or other metallic material which may be readily sealed to glass, and a glass tube 9 is hermetically sealed at each end to one of said discs. A plurality of pins I constituting anode arms arranged in a circle centered at the center of disc I project downwardly therefrom and an equal number of pins II similarly arranged project upwardly from the disc 8. In the central portionof the tube these pins de- :une a, circle in whichpins are equally spaced and alternately arranged as may be seen in Fig. 2. A cathode structure comprising a hollow tubular member I3 is positioned in the center of the circle dened by the pins I0 and II and spaced therefrom. Said cathode may be coated with a thermionically emissive coating adjacent said pins. A central bore I4 is provided in the pole piece 5 and the hollow tubular member I3 extends therethrough and is spaced therefrom. Within the hollow tubular member I3 is a heating coil I5 connected at its upper end to the tube I3 and at its lower end to a lead I6 which extends through the tubular member I3 and is sealed in a glass seal I'I closing the outer end of the tubular member I3. A metallic tube I8 of the same external diameter as the diameter of bore I4 lines the internal wall of the bore I4 and projects outwardly beyond the external face of pole piece 5. At its inner end the sleeve I 8 is hermetically sealed to the disc 8 and at its outer end is brazed or otherwise hermetically sealed to a tubular metal shell I9. The shell I9 is of 'a material such as Kovar which may be readily fused to glass and at its outer end is sealed to a glass tube 20. The tube 20 is sealed at its opposite end to a cup-shaped member 2l, which cup-shaped member 2I has an opening in its outer face through which the tubular member I3 extends and to which it is hermetically sealed. By this arrangement the cathode structure I3 is electrically insulated from the body I of the magnetron by means of glass sleeve 20. The externally projecting end of the cathode tube I3 may be connected to one pole of a source of heating current for cathode heating coil I5, the other pole being connected to the lead wire It.

In the operation of thedevice described in the foregoing, when the cathode heater I5 is energized and a suitable voltage supplied between the cathode and the anode structure, electrons emitted by the cathode into the annular space between the activated portion of the cathode and the anode arms are deflected by the magnetic iield, which is directed transversely to the paths of the electrons, as in conventional magnetrons, thereby generating oscillations within the anode structure. In this instance the body I provides a common inductive circuit between the anode elements I0 and II. To facilitate the conduction of the oscillating current over the interior sur face of the body i, this surface may be coated with a highly conductive material such as copper or silver. A portion of the oscillatory energy which is propagated in the interior chamber of the body i may be led of to a suitable utilization device by means of a coupling loop 22 which extends into the oscillatory field set up within said chamber. One end of the coupling loop 22 is connected to the inner end' of a conducting pipe 23 which extends through an opening in the body l. The other end of the coupling loop Z2 is connected to a conductor 2li which passes through the pipe 23 and constitutesl therewith a coaxial line. f

When the tube described inthe foregoing is oscillating the fingers i3 and il are of opposite phase so that oscillating currents tend to flow between alternate lingers HJ and il. The conducting circuit extends between each pin or linger lil and its adjacent finger ii which constitute capacitances. The circuits extend in a circular path through the wall of the body portion l. It will be seen that a portion of each circuit lies within the evacuated space ofthe tube 9 and the remaining portion is exterior of this space along the interior walls oi the body i. This circular path constitutes an inductance. Each of these circuits constitutes an oscillatory circuit whose natural frequency is determined by the inductance and capacity thereof. Since the fingers it and i i are :i

of opposite Voltage phase so that when the nger i@ is positive the adjacent linger Il is negative, and on the next half cycle voltage conditions are reversed, oscillatory current will flow between the lingers iii and I i through the walls of the annular chamber defined by the body I in a direction to create an annular magnetic eld in said chamber. All of said currents are in phase with each other, and thus all of said magnetic elds are likewise in phase, producing a strong resultant annular in the instance shown a tuning rod 25 may be l adjusted to project more'or less into the annular space within the body i. ln the instance shown the tuning rod 23 is threaded for adjustment longitudinally. However, the screw threads may be omitted and the` rod may slide toward or away from the interior chamber of the tube l. Since the space into which the tuning rod 25 projects is not a portion of the evacuated space of the tube, no provision need be made for hermetically sealing this rod relative to the wall through which it extends. Likewise no provision need be made for hermetically sealing the space .between the outer conductor 23 and the coaxialconductor 2e leading from the antenna loop 2, 2.

In the form of the invention-disclosed in Fig. 3 the inductive portion .of the oscillatory circuit is separate from the magnet 36. Referring to this figure, reference numeral 33 indicates a cupshaped member of copper or other non-magnetic and highly-conductive material. An end cap 3i closes one end of the cup-shaped member 30 and is provided with a central opening 32. A sleeve 23 surrounding the opening 32 projects into the cup-shaped member 3i), concentric with the upper portion of the circumferential wall thereof. The

4 bottom portion of the cup-shaped member 30 is provided with a corresponding opening 33. A pole piece 3a extends through the opening 32 and pron jects to a point slightly above the lower end of sleeve 23. A pole piece 35 is positioned at the bottom of the cup-shaped member 33 and in alignment with the opening 33. The interior end faces of the two pole pieces 34 and 35 are coextensive respectively with discs 31 and 38 oi' Kovar cr other material readily fusible with glass. A magnet 36 of Alnico or similar magnetic material connects the pole pieces 34 and 35. As in the previously described construction a glass tube 33 is hermetically sealed at each end to the discs 3l' and 33. The pins l0 and il are arranged in the same manner as pins i3 and Il in the previously described construction and also the cathode structure i3 is disposed in the same manner and constructed in the same way as the cathode i3 of Fig. l. In Fig. 3 the cathode is shown in side elevation, and it will be understood that the section therethrough would correspond with the sectional view of the cathode shown in Fig. l. It will be understood that the portion of cathode (i3 lying adjacent to the pins El and li is activated with an electron emissive material. Enlargements Il?. on the tubular member d3 at each end of the activated portion may be provided to conne the electrons to the annular space between the cathode and the juxtaposed portions of the arms 6B and lli. As in the previously described construction the cathode 43 is supported in a bore dll extending through the pole piece by a tubular member 48 hermetically sealed to the disc 33, the sleeve lli), glass seal 53, and the end cap 3i corresponding respectively to the parts i3, i3, 2S, and 2i of the previously described construction.

The operation of this form of the invention will be readily understood from the operation of the form previously described, and the output of the tube may be led oi by means of an antenna loop 52 connected at one end to a tubular conductor E3 and having the other end connected to a central conductor 5P, which tubular member 53 and central conductor 5ft comprise a coaxial line. In this instance the tuning of the oscillatory circuit is eiected by means -of an annular tuning piston 55 which may be moved inwardly or outwardly by means oi adjusting screws 53 to vary the inductive portion of the circuit externally of the evacuated space of the tube. In the instance shown the sleeve 23 surrounding the pole piece 3d forms a coaxial line with the circumferential wall of the upper portion of the cup-shaped member 33. The line so formed is terminated at its outer end by the annular tuning piston 55, thus permitting tuning over a wide range of frequencies.

ln the manufacture of devices as above described that portion c-i the device comprising the members deiining the evacuated space thereof and the members enclosed therein may be assembled as a. separate unit. This assembly unit comprises the discs 'l and 8 of Fig. l, the glass tube S together with the elements enclosed thereby and the sleeve I8 together with the sleeve i9, seal 23, and cup-shaped member 2i. This construction complete and evacuated may then be inserted into the body portion l through the opening provided for the pole piece lbeing centered by the bores provided for the two pole pieces. Pole piece 5 may then be inserted over the cathode seal and support assembly, the bore le being sufficientiy large for this purpose. The pole piece 5 may then be secured in position by any desired means, as by brazing or welding. It will be apparent that the device shown in Fig. 3 can be assembled in the same manner.

From the foregoing it will be apparent that both forms of the invention provide a magnetron in which the major portion of inductive part of the oscillatory circuit is exterior of the evacuated space oi the tube, and this inductive portion may be tuned within limits without the necessity of providing hermetic seals for the tuning means. Also the output of the tube may be taken from a portion of the enclosed space exterior of the evacuated space without the necessity for hermetic seals closing the output line.

What is claimed is:

l. An electronic discharge device for generating ultra-high frequency oscillations comprising an evacuated envelope, a cathode and a plurality of anode elements enclosed in said envelope, a hollow body of magnetic material defining an enclosed space surrounding said envelope and completing oscillatory circuits between said anode elements, said hollow body imposing a magnetic iield extending transversely to the direction of electron flow through the space between said cathode and said anode elements, and means in the space surrounding said envelope for tuning said oscillatory circuits.

2. An electronic discharge device comprising an evacuated envelope having a glass wall, a plurality of anode arms projecting into said envelope, a cathode positioned in said envelope in spaced relation to said anode arms, a hollow metallic body enclosing said envelope and electrically connecting said arms, said hollow metallic body being of magnetic material for imposing a magnetic field extending transversely to the direction oi electron iiow through the space between said cathode and said anode arms.

An electronic discharge device comprising an envelope having a tubular portion of glass, a pair oi metallic members hermetically sealing the ends of said tubular portion, a plurality of anode arms projecting into said envelope from each of said metallic members, a cathode projectinto said tubular portion through an opening in one of said metallic members, a cathode sealing and supporting structure hermetically sealing said opening and supporting said cathode in spaced relation to said anode arms, and a hollow metallic body enclosing said envelope, electrically connecting said metallic members to complete oscillatory circuits between said arms, and for imposing a magnetic eld transversely to the direction of electron flow between said cathode and said anode arms.

Li. An electronic discharge device comprising an envelope having a tubular portion of glass, a pair of metallic members hermetically sealing the ends of said tubular portion, a plurality of anode arms projecting into said envelope from each oi said metallic members, a cathode projecting into said tubular portion through an opening in one of said metallic members, a cathode sealing and supporting structure hermetically sealing said opening and supporting said cathode in spaced relation to said anode arms, a hollow body of magnetic material enclosing said envelope and connecting said metallic members to complete oscillatory circuits between said arms, said hollow body imposing a magnetic eld extending transversely to the direction of electron now between said cathode and said anode arms,

and means projecting into said hollow-A metallic body for tuning said oscillatory circuits.

5. An electronic discharge device comprising an envelope having a tubular portion of glass, a pair of metallic members hermetically sealing the ends of said tubular portion, a plurality of anode arms circularly mounted and projecting into said envelope from each of said metallic members, alternate of said arms being connected to one of said members and the intervening arms being connected to the other of said members, a cathode projecting into said tubular portion through an opening in one of said metallic members, a cathode sealing and supporting structure hermetically sealing said opening and supporting said cathode in spaced relation to said anode arms, a hollow metallic body enclosing and dening an annular space around said envelope, electrically connecting said metallic members to complete oscillatory 4circuits between said arms, and imposing a magnetic field Ibetween said cathode and anode arms in a direction transverse to the electron iiow therebetween, and an annular tuning piston adjustable in said annular space for tuning said oscillatory circuits.

6. An electronic discharge device comprising an envelope having a tubular portion of glass, a pair of metallic members hermetically sealing the ends of said tubular portion, a plurality of anode arms projecting into said envelope from each of said metallic members, a cathode projecting into said tubular portion through an opening in one of said metallic members, a cathode sealing and supporting structure hermetically sealing said opening and supporting said cathode in spaced relation to said anode arms, a hollow metallic body enclosing and delining an -annular space around said envelope, electrically connecting said metallic members to complete oscillatory circuits between said arms, and imposing a magnetic eld transversely of the direction of the electron ow between said cathode and anode arms, and an annular tuning piston adjustable in said annular space for tuning said oscillatory circuits.

7. An electronic discharge device for generating ultra-high frequency oscillations comprising an evacuated envelope, said envelope having a tubular portion of glass, upper and lower metallic members, one at each end of said tubular portion and hermetically sealed thereto, a cathode and a plurality of overlapping electron-receiving anode portions enclosed in said envelope, and means dening an enclosed space surrounding said envelope and completing oscillatory circuits between said anode portions, said anode portions projecting alternately from said upper and lower metallic members and being spaced from and concentrically disposed about said cathode, and said last-named means additionally imposing a magnetic field between said cathode and anode directed transversely to the direction of electron iiow between said cathode and said anode portions.

8. An electronic discharge device for generating ultra-high frequency oscillations comprising an evacuated envelope, said envelope having a tubular portion of glass, upper and lower metallic members, one at each end of said tubular .portion and hermetically sealed thereto, said metallic mem-bers each having a portion projecting exteriorly of said tubular portion, a cathode and a plurality of overlapping electron-receiving anode porti-ons enclosed in said envelope, and means contacting said metallic members deiining an enclosed space surrounding said envelope and completing oscillatory eircuits between said anode portions, said yanode portions projecting alternately from said upper and lower metallic vmerrfoers and being .spaced from and concentrically disposed about vsaid yc-z'atho'de, and Said lastnamed means additionally .imposing .a magnetic field between said cathode and anode directed transversely to the direction of electron now ine tween said cathode and .said anode portions.

9. An electric `discharge device comprising a lioll'oW cylindrical insulator, a fclosure member having a marginal `portion sealed to one end of 'said insulator and a flange defining a centrally located opening., a second closure member Asealed to the opposite end of said insulator, :a plurality oi elongated 1anolle elements mounted .in a circalai` array with the `individual elements extending in parallel .mutually spaced relation, Ialtenrrat'e y'ones :of said :anode elements being joined rrespee- .tively to the closure .members .sealed to 'opposite Aends of said insulator, an annular 'polepi'ece supported adjacent `said flange, and a 'cathode supported from said .pole piece.

WILLIAM C.

REFERENCES CITED The foliowing references are of record in the file ol* this patent:

UNITED STATES PATENTS Number Name Date 2,115,521 `tz et al Apr. 26 1938 2,241,976 Blewett et al. May 13, 1941 ?,248.,'712 Litton July 8, .1941 2,252,118 Dallenbach et; al. Aug.12, 1941 2,391,016 Gunzton et al Dec. 18, 1945 2,421,636 McArthur et al. June 3, 1947 2,424,886 Hansell July 29, 1947 2,428,888 Nelson Oct. 14, 1947 `.2,4Z. 2,4'66 Burns Dec.. 9, 1'947 FOREIGN PATENTS Number' Country Date 509,102 Great .Britain July 11, 1'939 

